The typical rotor for a rotary press is composed of a die plate and an upper and a lower punch guiding for upper and lower punches, which co-operate with bores in the die plate. The rotor is driven around a vertical axis by a suitable driving motor, and the powder-shaped material filled into the die bores by a filling device is pressed together by the punches. The pressing together takes place in the so-called pressing stations, in which are arranged at least one upper and one lower pressing roller at a time, which act on the punch heads. In the remaining rotation phases, the punches are guided by suitable punch cams, amongst others for ejecting the pressed articles by cams controlling the lower punches. Such rotors have become known from U.S. Pat. No. 5,004,413, DE 101 59 114 A1 or DE 10 2004 040 163 B3, the entire contents of each of these references are incorporated herein by reference.
Usually, the upper and lower punches consist of a shaft, a head co-operating with the pressing rollers and a tool portion, which sinks into the die bores. The mostly cylindrical shaft is guided in corresponding bores of the punch guidings. For the purpose that the punches do not rotate in the bores, it is also known to provide a parallel key which co-operates with a parallel key groove in order to prevent a rotation of the punches.
In order not to affect the guiding property, it is also known to provide sealings which prevent that pressing material arrives between the guiding bores and the punch shaft and lubricant leaks out. The sealing is not possible in the region of a parallel key groove. Thus, the punch shaft must not be moved through a sealing in the region of the parallel key groove.
The present invention is based on the objective to provide a rotor for a rotary tablet press in which a simple, sealed guiding of the pressing punches is made possible.